Monday, December 10, 2012

I built a system to synchronize the two color wheel motors in a Wurlitzer Model 1015 jukebox. Originally, the jukebox used two synchronous clock motors, and the designers assumed that the motors would stay synchronous and keep the colors wheels at the same orientation after manually setting it. As it turns out, the torque required to spin the color wheels is enough to cause the motors to slip. Eventually, the color wheels get out of sync, and the left and right side of the jukebox do not match in color.

My upgraded system uses two small DC gearmotors that interface with the original drive mechanics via a nylon gear from McMaster. I drive the two motors via a PN2222A transistor and sense the position of the color wheels with the optical sensors from an old computer mouse. An arduino controls the motors via PWM (20 or 30 KHz), and runs a phase-locked-loop routine with P-I control. This system could use a little tuning, but it's pretty close.